Took it to the local dealer in Norfolk Va.
Codes showed throttle body issue and part replaced.
2 weeks later same issue, took back in and had the "wiring" replaced per senior GM tech advisor.

Ran fine until over the weekend when I was towing my boat across the cheasepeake bay bridge with the ac on and it powered down to max of 10mph in the first tunnel....lots of fun...Turned engine off and restarted it and it ran ok for about 30minutes with ac on and same thing. May be coincidental but once i turned the ac was turned off it did not happen again, but i was turned around by that point and was close to home. CK engine light off and reduced engine power off this am.

Fuel to the flame......Turns out when the truck was under warranty from prior owner and the throttle had already been replaced about 10K before i bought it....although i did not see record of this on car fax!

I'm thinking it may be a MAF problem. I've heard of power issues due to a problem with the mass airflow sensor. That may have caused the code for throttle body issue. I still consider myself a novice on EFI engines though so it's just a thought. I'm probably way off but it may be something to look into. Are there any other symptoms that you notice? Noises, smells, etc...?

thanks for the insight....spoke to dealer yesterday and they said "more wiring needs to be replaced"....which sounds to me like they are not sure what is really going on with the truck.....in response to the early suggestions....there has been no abnormal noises or smells and the truck runs fine btwn these recurring episodes.....i appreciate the suggestions.....better ideas then the "pro's" have offered.